1. Field of the Invention
The present invention relates to an injection molding machine controlled by means of a processor, and more particularly, to an injection pressure monitoring method for injection condition setting.
2. Description of Related Art
In an injection stage of an injection molding machine, injection speed control is effected such that the injection speed is changed by stages in accordance with the screw position. Since the flow resistance of a resin moving in a mold cavity varies depending on the region where the resin passes, it is advisable to set the injection speed changeover position and the speed of each stage in accordance with the change of the flow resistance. To attain this, it is necessary to grasp the filling state of the resin in the mold cavity which corresponds to the screw position in the injection stroke.
Conventionally, the short-shot method or the like has been used as a method for examining the filling state of the resin in the mold cavity. According to this method, the mold is opened to examine the resin fill after injecting the resin in a small amount, and the injection quantity is then gradually increased. By doing this, the screw positions where the flow resistance changes are obtained according to the actual position of the resin loaded in the mold, and the injection speed changeover position is obtained on the basis of the screw position.
In this short-shot method, as described above, it is necessary to increase the injection quantity of the resin little by little, and to open the mold to examine the leading end position of the resin in the mold with every cycle of injection. This requires much time and labor. In some molds for molding connectors and the like, moreover, the resin may be excessively loaded while operating conditions are being set by the short-shot method, arousing a problem.